1. Field of the Invention
The present invention relates to a device with a spring return, able to operate without friction, to actuate a reciprocable component. This system is applicable particularly, though not exclusively, to the return of a slide of the kind used in hydraulic distributors such as those used in circuits controlling jacks, valves, pumps, or hydraulic motors, etc. Such hydraulic circuits are used in connection with machine tools and workshop equipment, in the aeronautical industry and in various other branches of industry.
2. Description of the Prior Art
There are known slide-type hydraulic distributors in which the slide has, at one end, two cup-shaped rings with a helical spring compressed between the rings. Each of these two rings contacts a fixed wall in the stator. When the slide is not under control, it is maintained in a central position by the spring, and it is reciprocable between positions on opposite sides of the central position when it is being controlled.
In practice, friction arises during the movement of the slide, between the spring and the rings, and between the rings and the corresponding zones of the slide. This friction may lead to the appearance of high spots, which may be particularly inconvenient in the case of a distributor whose slide has its axial movement controlled by a variable pilot pressure. In fact, at any moment, the axial position of the slide is defined by the balance of two opposing forces, namely the thrust at that moment of the spring, and the force exercised by the pilot pressure. When the pilot pressure is itself variable, the variable thrust force which results from it must be balanced by the resistance force of the spring, and it will be seen that the balance may be distorted if friction resistances appear.